Angle detection apparatus

ABSTRACT

Provided is an angle detection device capable of detecting the angle with high sensitivity by a very simple assembly process without requiring complicated processing. The angle detection device is provided with: a rotor ( 5 ) which is formed by a disk plate body produced from a magnetic substance having uniaxial magnetic anisotropy, the disk plate body rotating around a center point within the disk plate surface; a stator ( 3 ) which is provided to face the plate surface of the disk plate body of the rotor ( 5 ), has approximately the same external shape as that of the rotor, and is divided into a plurality of fan-shaped regions, and in which an exciting coil or a detection coil is wound along the outer periphery of each of the divided regions.

RELATED APPLICATIONS

This patent application is a reissue of U.S. Pat. No. 9,134,108, whichissued on Sep. 15, 2015 which is a continuation of InternationalApplication No. PCT/JP2011/063249, filed on Jun. 9, 2011, entitled,“Angle Detection Apparatus,” which claims priority to Japanese PatentApplication No. 2010-152396, filed on Jul. 2, 2010, and Japanese PatentApplication No. 2011-067830, filed on Mar. 25, 2011, the contents andteachings of each of which are hereby incorporated by reference in theirentirety.

FIELD

The present innovation relates to an angle detection apparatus formaking an angle detection.

BACKGROUND

In order to control a driving motor, which is used for drive of forexample an automobile, a robot, etc, it is necessary to detect arotation angle of a rotor with a high degree of accuracy. A resolver haswidely been used as an apparatus for detecting a rotation angle of therotor. The resolver, which has currently been used, mainly has astationary unit and a rotation unit, and irregularity, deviation, etc.of the stationary unit may be utilized to detect a rotation angle (seefor example Japanese Patent Provisional Publication No. 2009-128133(Patent Document 1) and Japanese Patent Provisional Publication No.2008-29070 (Patent Document 2)).

Patent Document 1 shows an art of a resolver, which comprises aplurality of magnetic cores with wound wires, a stator having aplurality of members with wound wires, which are provided around therespective magnetic cores, and a rotor provided rotatably relative tothe stator, at least one of the plurality of members with would wiresbeing a sheet-shaped coil in which a conductive material is patterned ina spiral manner on a sheet, and at least a portion of the surface of thesheet on which the conductive material is pattern-formed, or the backsurface thereof facing a side surface of the above0mentioned magneticcores with would wires, and also shows a structure of the rotor havingfour projections and an eccentric structure relative to an axis.

Patent Document 2 shows an art of a structure in which the inner surfaceof a curved gap formation plate, which is provided on the inner surfaceof a ring-shaped rotor plate, is placed to face a plurality ofstator-wound wires on a ring-shaped stator plate, to obtain anglesignals varying in a sine wave shape.

SUMMARY

However, the arts disclosed in Patent Documents 1 and 2 have muchdifficulty in adjustment of the shape of the projections of the rotorand adjustment of eccentricity, and a working operation for the innersurface of the curved gap formation plate, which is provided on theinner surface of the rotor plate. Extremely precise and complicatedworking and assembling operation are required to manufacture theresolver, which permits to detect a rotation angle with a high degree ofaccuracy, thus requiring much effort and time for the operation.

An object of the present innovation is to provide an angle detectionapparatus, which permits to detect an angle with a high degree ofaccuracy, and may be assembled in an extremely easy manner, without theneed for a complicated working operation.

An angle detection apparatus disclosed in the present applicationcomprises: a rotor in which a disk member comprising a magnetic body hasa magnetic permeability, which is generally uniaxially anisotropic, thedisk member being rotatable around a central point in a plane of thedisk member; and a stator comprising a plurality of coils, at least oneof the coils being an exciting coil that generates a magnetic field, andat least one of the coils being a detection coil that intersects withthe magnetic field excited by the exciting coil to detect a voltagecorresponding to an angle of rotation of the rotor.

In the angle detection apparatus disclosed in the present application,rotation of the rotor, which is constituted as the disk member havinggenerally a uniaxial anisotropy causes permeance relative to a rotationangle to vary in a sine wave. More specifically, when the rotor rotatesone revolution, inductance of the detection coil varies in a sine wave,and an angle may be detected based on the fact that each mechanicalrotation of the rotor at an angle of 180 degrees causes variation in asine wave in an electrical angle of 360 degrees. There are effects ofproviding an extremely simple structure, avoiding complicated workingand assembling operation, thus permitting a manufacture in a very easymanner and at a low cost.

The angle detection apparatus disclosed in the present application mayhave a structure in which the stator has substantially a same outershape as the disk member of the rotor and is disposed in a vicinity ofthe disk member of the rotor so as to face the plane thereof, the statorbeing divided into a plurality of fan-shaped sections, and the excitingcoil and the detection coil being provided alternately on at leastlinear portion of the fan-shaped sections, respectively, on an outerperiphery of the fan-shaped sections.

The angle detection apparatus disclosed in the present application has aplane structure in which the stator is placed so as to face the surfaceof the disk member of the rotor, without providing the stator so as toface an outer surface of the disk member of the rotor. This may providean effect of decreasing the thickness in a simple manufacturing process,without deteriorating the functions.

The angle detection apparatus disclosed in the present application mayfurther comprise a back yoke that is provided on an opposite side to therotor relative to the stator, the back yoke having substantially a sameouter shape as a disk member of the stator and being placed so as toface the disk member thereof.

In the angle detection apparatus disclosed in the present application,there is provided the back yoke that is provided on an opposite side tothe rotor relative to the stator, the back yoke having substantially thesame outer shape as the disk member of the stator and being placed so asto face the disk member thereof, thus providing effects of enhancing amagnetic field and improving a detection sensitivity. This back yoke maybe considered as a part, which is integral with the stator.

The angle detection apparatus disclosed in the present application mayhave a structure in which the stator is divided into four fan-shapedsections having substantially a same outer shape; coils, which areprovided on at least linear portions of the fan-shaped sections,respectively, on an outer periphery of a set of fan-shaped sections oftwo sets of fan-shaped sections each of which face each other relativeto a central point of a disk member of the stator, are used as thedetection coil, and coils, which are provided on at least linearportions of the fan-shaped sections, respectively, on an outer peripheryof other set of fan-shaped sections of the two sets of fan-shapedsections, are used as the exciting coil; and in the set of thefan-shaped sections on which the exciting coils are provided, theexciting coils are placed so as to generate a magnetic field in whichthe exciting coils provided on the respective fan-shaped sections areopposite to each other in polarity, and in the other set of thefan-shaped sections on which the detection coils are provided, thedetection coils are placed so that the detection coils provided on therespective fan-shaped sections are opposite to each other in polarity.

In the angle detection apparatus disclosed in the present application,the stator is divided into four fan-shaped sections having substantiallya same outer shape; coils, which are provided on at least linearportions of the fan-shaped sections, respectively, on the outerperiphery of the set of fan-shaped sections each of which face eachother, are used as the detection coil, and coils, which are provided onat least linear portions of the fan-shaped sections, respectively, on anouter periphery of the other set of fan-shaped sections each of whichface each other, are used as the exciting coil; and in the set of thefan-shaped sections on which the exciting coils are provided, theexciting coils are placed so as to generate a magnetic field in whichthe exciting coils provided on the respective fan-shaped sections areopposite to each other in polarity, and in the other set of thefan-shaped sections on which the detection coils are provided, thedetection coils are placed so as to generate a magnetic field in whichthe detection coils provided on the respective fan-shaped sections areopposite to each other in polarity. This may provide effects ofutilizing a combination of the exciting coil and the detection coilbased on characteristic properties in an easy axis direction and a hardaxis direction of the uniaxial anisotropy to make an angle detectionwith a cycle of 180 degrees.

The angle detection apparatus disclosed in the present application mayhave a structure in which the stator is divided into eight fan-shapedsections as divided having substantially a same outer shape, of theeight fan-shaped sections as divided, at least three fan-shaped sectionsare placed closely to each other so as to face the plane of the rotor ina combined state of the fan-shaped sections, and two of the detectioncoils and one of the exciting coil are provided alternately on at leastlinear portion of the fan-shaped sections, respectively, on an outerperiphery of the three fan-shaped sections as divided.

In the angle detection apparatus disclosed in the present application,the stator is divided into eight fan-shaped sections as divided havingsubstantially the same outer shape, of the eight fan-shaped sections asdivided, at least three fan-shaped sections are placed closely to eachother so as to face the plane of the rotor in a combined state of thefan-shaped sections, and two of the detection coils and one of theexciting coil are provided alternately on at least linear portion of thefan-shaped sections, respectively, on the outer periphery of the threefan-shaped sections as divided. This makes it possible to detectaccurately a sine component and a cosine component by the minimum needednumber of parts of the stator, thus providing an effect of detecting anangle of the rotor with a high degree of accuracy. Especially, aconfiguration in which dedicated integrated circuits are used to obtainan arc tangent of a biphase output voltage may provide an effect ofsimplifying a manufacturing process to improve the manufactureefficiency.

The angle detection apparatus disclosed in the present application mayfurther comprise: a back yoke that is provided on an opposite side tothe rotor relative to the stator, the back yoke having substantially asame outer shape as the disk member of the stator and being placed so asto face the disk member thereof, the back yoke being provided so as tocover at least a place in which the fan-shaped sections as divided areplaced closely to each other.

In the angle detection apparatus disclosed in the present application,there is further comprised the back yoke that is provided on theopposite side to the rotor relative to the stator, the back yoke havingsubstantially the same outer shape as the disk member of the stator andbeing placed so as to face the disk member thereof, the back yoke beingprovided so as to cover at least the place in which the fan-shapedsections as divided are placed closely to each other. This structure inwhich the back yoke is placed only a region having the strongestconnection between the coils may provide an effect of maintain adetection accuracy of angle by the minimum needed area of the back yoke.

The angle detection apparatus disclosed in the present application mayhave a structure in which the stator is divided into sixteen fan-shapedsections having substantially a same outer shape, of a set of eightfan-shaped sections as placed closely to each other, a set of fourfan-shaped sections, which face each other in a cross-shapedrelationship relative to a central point of a disk member of the stator,detects a sine component, and other set of four fan-shaped sectionsdetects a cosine component.

In the angle detection apparatus disclosed in the present application,the stator is divided into sixteen fan-shaped sections havingsubstantially the same outer shape, of the set of eight fan-shapedsections as placed closely to each other, the set of four fan-shapedsections, which face each other in a cruciform relationship relative tothe central point of the disk member of the stator, detects the sinecomponent, and the other set of four fan-shaped sections detects thecosine component. This structure may provide an effect of obtainingeasily an angle of rotation based on the biphase signal. Especially, aconfiguration in which dedicated integrated circuits are used to obtainan arc tangent of a biphase output voltage may provide an effect ofsimplifying a manufacturing process to improve the manufactureefficiency.

The angle detection apparatus disclosed in the present application mayfurther comprise: a back yoke that is provided on an opposite side tothe rotor relative to the stator, the back yoke having substantially asame outer shape as the disk member of the stator and being placed so asto face the disk member thereof, the back yoke being divided into eightfan-shaped sections having substantially a same outer shape in acorresponding manner to the set of eight fan-shaped sections of thestator, and a gap is provided between adjacent two of the fan-shapedsections.

In the angle detection apparatus disclosed in the present application,the back yoke is divided into eight fan-shaped sections havingsubstantially the same outer shape in the corresponding manner to theset of eight fan-shaped sections of the stator, and the gap is providedbetween adjacent two of the fan-shaped sections. This structure in whichthe back yokes are placed only respective regions having the strongestconnection between the coils may provide an effect of maintain adetection accuracy of angle by the minimum needed area of the backyokes.

The angle detection apparatus disclosed in the present application mayhave a structure in which two fan-shaped sections having a central angleof 45 degrees, of a plurality of fan-shaped sections as divided, whichis obtained by dividing a disk member having substantially a same outershape as the disk member of the rotor, are placed, as a fan-shapedsection as divided for excitation, so as to face each other relative toa central point of the disk member, exciting coils are provided on atleast linear portion thereof, respectively, on an outer periphery of thefan-shaped section as divided for excitation so as to generate magneticfields, which are opposite to each other in polarity; two of thefan-shaped sections as divided being provided, as a sine detectionfan-shaped section, adjacently to the fan-shaped section as divided forexcitation, so as to face each other relative to a central point of thedisk member, the detection coil that detects a sine component beingprovided on at least linear portion on an outer periphery of the sinedetection fan-shaped section, so as to be opposite to each other inpolarity; and two of the fan-shaped sections as divided being provided,as a cosine detection fan-shaped section, adjacently to the fan-shapedsection as divided for excitation, on an opposite side of the sinedetection fan-shaped section via the fan-shaped section as divided forexcitation so as to face each other relative to a central point of thedisk member, the detection coil that detects a cosine component beingprovided on at least linear portion on an outer periphery of the cosinedetection fan-shaped section, so as to be opposite to each other inpolarity.

In the angle detection apparatus disclosed in the present application,the two fan-shaped sections having a central angle of 45 degrees areplaced so as to face each other relative to the central point of thedisk member, the exciting coils are provided on the outer periphery ofthe fan-shaped section so as to generate magnetic fields, which areopposite to each other in polarity; the two sine detection fan-shapedsections are provided adjacently to the fan-shaped section as dividedfor excitation, so as to face each other relative to the central pointof the disk member, the detection coil that detects a sine component isprovided on the outer periphery of the sine detection fan-shapedsection, so as to be opposite to each other in polarity; the twofan-shaped cosine detection fan-shaped section are placed on an oppositeside of the sine detection fan-shaped section via the fan-shaped sectionas divided for excitation so as to face each other relative to thecentral point of the disk member, and the detection coil that detects acosine component is provided on the outer periphery of the cosinedetection fan-shaped section, so as to be opposite to each other inpolarity. This makes it possible to detect accurately a sine componentand a cosine component, thus providing an effect of detecting an angleof the rotor with a high degree of accuracy.

The angle detection apparatus disclosed in the present application mayhave a structure in which the stator comprises fan-shaped sections asdivided which is obtained by dividing the stator into a plurality offan-shaped sections; four fan-shaped sections as divided each having acentral angle of 45 degrees of the fan-shaped sections as divided beingprovided, as a fan-shaped section as divided for excitation, so as toface each other in a cruciform relationship relative to a central pointof the disk member, the exciting coils being provided on the at leastlinear portion so that a direction of a magnetic field, which passesthrough an inside of two fan-shaped sections as divided for excitationof the four fan-shaped sections as divided for excitation is positiveand a direction of a magnetic field, which passes through an inside ofother two fan-shaped sections as divided for excitation thereof isnegative; four fan-shaped sections as divided being provided, as a sinedetection fan-shaped section, so as to be adjacent to the fan-shapedsection as divided for excitation and so as to face each other in acruciform relationship relative to the central point of the disk member,a sine detection coil, which detects a sine component, being provided onat least the linear portion, which is adjacent to the fan-shaped sectionas divided for excitation, on an outer periphery of the sine detectionfan-shaped section as provided, and two of the sine detection coilsbeing aligned in a positive direction and other two of the sinedetection coils being aligned in a negative direction; and fourfan-shaped sections as divided being provided, as a cosine detectionfan-shaped section, so as to be adjacent to the fan-shaped section asdivided for excitation on an opposite side to the sine detectionfan-shaped section via the fan-shaped section as divided for excitation,and so as to face each other in a cruciform relationship relative to thecentral point of the disk member, a cosine detection coil, which detectsa cosine component, being provided on at least the linear portion, whichis adjacent to the fan-shaped section as divided for excitation, on anouter periphery of the cosine detection fan-shaped section as provided,and two of the cosine detection coils being aligned in a positivedirection and other two of the cosine detection coils being aligned in anegative direction.

In the angle detection apparatus disclosed in the present application,the four fan-shaped sections as divided for excitation each having thecentral angle of 45 degrees are provided, so as to face each other inthe cruciform relationship relative to the central point of the diskmember, the exciting coils are provided so that the direction of themagnetic field, which passes through then inside of two fan-shapedsections as divided for excitation of the four fan-shaped sections asdivided for excitation is positive and the direction of the magneticfield, which passes through the inside of other two fan-shaped sectionsas divided for excitation thereof is negative; the four sine detectionfan-shaped sections are provided so as to be adjacent to the fan-shapedsection as divided for excitation and so as to face each other in thecruciform relationship relative to the central point of the disk member,the sine detection coil, which detects the sine component, is providedon the outer periphery of the sine detection fan-shaped section, the twoof the sine detection coils are aligned in the positive direction andother two of the sine detection coils are aligned in the negativedirection; and the four cosine detection fan-shaped sections areprovided so as to be adjacent to the fan-shaped section as divided forexcitation on an opposite side to the sine detection fan-shaped sectionvia the fan-shaped section as divided for excitation, and so as to faceeach other in the cruciform relationship relative to the central pointof the disk member, and the cosine detection coil, which detects acosine component, is provided on the outer periphery of the cosinedetection fan-shaped section, and the two of the cosine detection coilsare aligned in the positive direction and the other two of the cosinedetection coils are aligned in the negative direction. This makes itpossible to detect accurately a sine component and a cosine component,thus providing an effect of detecting an angle of the rotor with a highdegree of accuracy.

The angle detection apparatus disclosed in the present application mayfurther comprise: a back yoke that is provided on an opposite side tothe rotor relative to the stator, the back yoke being provided so as tocover at least a close area between the fan-shaped sections as dividedfor excitation and the sine detection coil, which are placed closely toeach other, and a close area between the fan-shaped sections as dividedfor excitation and the cosine detection coil.

In the angle detection apparatus disclosed in the present application,there is further comprised the back yoke that is provided on theopposite side to the rotor relative to the stator, the back yoke beingprovided so as to cover at least the close area between the fan-shapedsections as divided for excitation and the sine detection coil, whichare placed closely to each other, and the close area between thefan-shaped sections as divided for excitation and the cosine detectioncoil. This structure in which the back yoke is placed only a regionhaving the strongest connection between the coils may provide effects ofmaintain a detection accuracy of angle by the back yoke composed of theminimum needed parts thereof and of obtaining a magnetic connectionhaving a locally strong area, thus making it possible to detectindependently a sine component and a cosine component even in a placewhere the cosine detection coils and the sine detection coils are placedtogether, and particularly in a region of the central portion of thedisk member composed of the fan-shaped sections.

The angle detection apparatus disclosed in the present application mayhave a structure in which the back yoke has substantially asemicylindrical shape, one of edges thereof being placed adjacently tothe fan-shaped sections as divided for excitation and other of the edgesthereof being placed adjacently to the sine detection coil or the cosinedetection coil.

In the angle detection apparatus disclosed in the present application,the back yoke has substantially the semicylindrical shape, one of edgesthereof being placed adjacently to the fan-shaped sections as dividedfor excitation and the other of the edges thereof being placedadjacently to the sine detection coil or the cosine detection coil. Thismay provide an effect of permitting to obtain a strong magneticconnection, while controlling the magnetic resistance in a closed pathin which the magnetic field makes the circuit, to detect independently asine component and a cosine component.

The angle detection apparatus disclosed in the present application mayhave a structure in which there are provided as the stator two statorsbetween which the rotor is placed, the stators facing the rotor; thestator is stationary with a shifted phase of 45 degrees in a plane.

In the angle detection apparatus disclosed in the present application,there are provided as the stator two stators between which the rotor isplaced, the stators facing the rotor; the stator is stationary with ashifted phase of 45 degrees in a plane, i.e., in a state in which itturns 45 degrees around the central axis. This makes it possible todetect accurately a sine component and a cosine component, thusproviding an effect of detecting an angle of the rotor with a highdegree of accuracy. Particularly, use of the two stators, which permitto provide an output of modulation wave suppressed where appropriate,makes it possible to detect the angle with an extremely high degree ofaccuracy.

The angle detection apparatus disclosed in the present application mayhave a structure in which there are provided as the stator two statorswith an aligned phase, and the rotor is placed between the two statorswith a shifted uniaxial anisotropy of 45 degrees in a plane and bondedto the stators.

In the angle detection apparatus disclosed in the present application,there are provided as the stator two stators with the aligned phase, andthe rotor is placed between the two stators with the shifted uniaxialanisotropy of 45 degrees in the plane, i.e., in a state in which itturns 45 degrees around the central axis and bonded to the stators. Thismakes it possible to detect accurately a sine component and a cosinecomponent, thus providing an effect of detecting an angle of the rotorwith a high degree of accuracy. Particularly, use of the two stators,which permit to provide an output of modulation wave suppressed whereappropriate, makes it possible to detect the angle of the rotor with anextremely high degree of accuracy.

The angle detection apparatus disclosed in the present application mayhave a structure in which there are provided as the stator two statorswith a shifted phase of 45 degrees in a plane, and the rotor is placedbetween the two stators so that the stators face the plane of the rotorand bonded to the stators.

In the angle detection apparatus disclosed in the present application,there are provided as the stator two stators with the shifted phase of45 degrees in the plane, i.e., in a state in which it turns 45 degreesaround the central axis and bonded to the stators, and the rotor isplaced between the two stators so that the stators face the plane of therotor and bonded to the stators. This makes it possible to detectaccurately a sine component and a cosine component, thus providing aneffect of detecting an angle of the rotor with a high degree ofaccuracy. Particularly, use of the two stators, which permit to providean output of modulation wave suppressed where appropriate, makes itpossible to detect the angle of the rotor with an extremely high degreeof accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 includes a set of overall views of an angle detection apparatusaccording to the first embodiment of the present innovation;

FIG. 2 includes a set of views illustrating respective parts of theangle detection apparatus according to the first embodiment of thepresent innovation;

FIG. 3 is a view illustrating a principle of an angle detection of theangle detection apparatus according to the first embodiment of thepresent innovation;

FIG. 4 includes a set of views illustrating an angle dependency of acomponent (H//) contributing to magnetization in an exciting magneticfield H by which a magnetic body having a uniaxial anisotropy is to bemagnetized, of the angle detection apparatus according to the firstembodiment of the present innovation, and illustrating progress of themagnetization;

FIG. 5 is a view illustrating an output voltage waveform of the angledetection apparatus according to the first embodiment of the presentinnovation;

FIG. 6 includes a set of views illustrating an angle detection by theangle detection apparatus according to the first embodiment of thepresent innovation;

FIG. 7 includes a set of views illustrating a formation process of arotor of the angle detection apparatus according to the first embodimentof the present innovation;

FIG. 8 includes a set of views illustrating respective parts of theangle detection apparatus according to the second embodiment of thepresent innovation;

FIG. 9 includes a set of views illustrating an angle detection by theangle detection apparatus according to the second embodiment of thepresent innovation;

FIG. 10 is a view illustrating an output voltage waveform of the angledetection apparatus according to the second embodiment of the presentinnovation;

FIG. 11 includes a set of views illustrating respective parts of theangle detection apparatus according to the third embodiment of thepresent innovation;

FIG. 12 includes a set of views showing output results of the angledetection apparatus according to the third embodiment of the presentinnovation;

FIG. 13 includes a set of views illustrating respective parts of theangle detection apparatus according to the fourth embodiment of thepresent innovation;

FIG. 14 is a top plan view in case where the respective parts of theangle detection apparatus according to the fourth embodiment of thepresent innovation are assembled together;

FIG. 15 includes a set of views illustrating a stator of the angledetection apparatus according to the fifth embodiment of the presentinnovation;

FIG. 16 includes a first set of views illustrating a stator of the angledetection apparatus according to the fifth embodiment of the presentinnovation;

FIG. 17 includes a second set of views illustrating the stator of theangle detection apparatus according to the fifth embodiment of thepresent innovation;

FIG. 18 includes a set of views illustrating a back yoke of the angledetection apparatus according to the sixth embodiment of the presentinnovation;

FIG. 19 includes a set of views showing output results of the angledetection apparatus according to the sixth embodiment of the presentinnovation;

FIG. 20 is a cross-sectional view of the angle detection apparatusaccording to the seventh embodiment of the present innovation;

FIG. 21 is a first view illustrating a structure of a stator and a rotorof the angle detection apparatus according to the seventh embodiment ofthe present innovation;

FIG. 22 is a second view illustrating a structure of a stator and arotor of the angle detection apparatus according to the seventhembodiment of the present innovation;

FIG. 23 includes a set of views illustrating a stator of the angledetection apparatus according to the eighth embodiment of the presentinnovation and illustrating a cross-section thereof;

FIG. 24 includes a set of cross-sectional views of the angle detectionapparatus according to the ninth embodiment of the present innovation;and

FIG. 25 includes a set of cross-sectional views of the angle detectionapparatus according to the tenth embodiment of the present innovation.

DETAILED DESCRIPTION

First Embodiment of the Present Innovation

An angle detection apparatus according to the embodiment of the presentinnovation will be described with reference to FIGS. 1 to 7. FIG. 1includes a set of overall views of the angle detection apparatusaccording to the first embodiment of the present innovation, FIG. 2includes a set of views illustrating respective parts of the angledetection apparatus according to the first embodiment of the presentinnovation, FIG. 3 is a view illustrating a principle of an angledetection of the angle detection apparatus according to the firstembodiment of the present innovation, FIG. 4 includes a set of viewsillustrating an angle dependency of a component (H//) contributing tomagnetization in an exciting magnetic field H by which a magnetic bodyhaving a uniaxial anisotropy is to be magnetized, of the angle detectionapparatus according to the first embodiment of the present innovation,and illustrating progress of the magnetization, FIG. 5 is a viewillustrating an output voltage waveform of the angle detection apparatusaccording to the first embodiment of the present innovation, FIG. 6includes a set of views illustrating an angle detection by the angledetection apparatus according to the first embodiment of the presentinnovation and FIG. 7 includes a set of views illustrating a formationprocess of a rotor of the angle detection apparatus according to thefirst embodiment of the present innovation.

The angle detection apparatus according to the embodiment of the presentinnovation comprises a rotor which is composed of a disk member, whichis uniaxially anisotropic, and is rotatable around the central point ina plane of the disk member; and a stator comprising a plurality ofcoils, at least one of the coils being an exciting coil that generates amagnetic field, and at least one of the coils being a detection coilthat intersects with the magnetic field excited by the exciting coil todetect a voltage corresponding to an angle of rotation of the rotor. Thestator has substantially the same outer shape as the disk member of therotor and is disposed so as to face the plane of the disk memberthereof. The stator is divided into two fan-shaped sections (orsemicircular sections) and the exciting coil or the detection coil iswound along the outer periphery of the respective divided regions. Inaddition, a back yoke, which has substantially the same outer shape asthe disk member of the stator, is provided on the opposite side to therotor so as to face the disk member thereof.

In the present innovation, the stator is composed of the fan-shapedsections, which are provided by dividing a stationary member having thesame outer shape as the disk member of the rotor radially from thecentral point thereof into the fan-shaped sections, winding the excitingcoil or the detection coil along the outer periphery of the respectivefan-shaped sections as divided or winding the exciting coil or thedetection coil along the outer periphery of the stationary member of thefan-shaped sections and assembling the fan-shaped sections intosubstantially the same outer shape as the disk member of the rotor. Thestationary member around which the coil is wound may be formed of amagnetic material or a magnetic material may be disposed on the plane ofthe stationary member.

FIG. 1(A) is a perspective view of the angle detection apparatus 1according to the embodiment of the present innovation, FIG. 1(B) is across-sectional view, of the angle detection apparatus 1, cut along theline I-I with arrows in FIG. 1(A) and FIG. 2 includes the respective topplan views of the back yoke 2, the stator 3 and the rotor 5 of the angledetection apparatus 1 according to the embodiment of the presentinnovation. The angle detection apparatus 1 has the rotor 5, which iscomposed of a disk member, which is uniaxially magnetic anisotropic, andis rotatable around the central point 5a to which a rotation shaft 6 isconnected, in a plane of the disk member; the stator 3, which hassubstantially the same outer shape and is placed so as to face the diskmember of the rotor 5 in a non-contact state; and the back yoke 2, whichis formed of a (isotropic) magnetic thin plate having no orientationinto substantially the same outer shape as the stator 3, and is placedin a contact or non-contact state with the stator 3, so as to face thesurface of the stator 3 on the opposite side of which surface the rotor5 is placed. The back yoke 2 is actually the disk member havingsubstantially the same outer shape as the stator, although the back yoke2 is shown in FIG. 1(A) as having the semicircular shape forfacilitation of understanding. The back yoke 2 is not always required,but is preferably provide to enhance the coupling of the magnetic flux.

The stator 3 is divided into the semicircular shape (3a, 3b) and thedetection coil 4a (referred also to as “S1”) and the exciting coil 4b(referred also to as “P1”) are would on the respective side areas of thesections 3a, 3b. The detection coil 4a and the exciting coil 4b are forexample coils of copper wire with a diameter of 0.1 mm of 100 turns. Theback yoke 2 is capable of causing the magnetic flux generated by theexciting coil 4b to intersect effectively with the detection coil 4a,thus improving sensitivity. As the back yoke 2, there may be used onethat is obtained for example by piling up some thin sheets of amorphousmagnetic strips having a width of 5 cm and bonding them, and cutting thebonded sheets into a disk shape. Alternatively, there may be usedanother one that is formed for example of thin sheets of permalloyhaving a thickness of about 0.1 mm to 2 mm.

The rotor 5 is formed of the disk member in which a magnetic plate or amagnetic composite plate having a uniaxially magnetic anisotropy in thedirection of the plane of the disk member (i.e., the direction of thearrow as shown in FIG. 1(A) and FIG. 2(C)) is joined at the centralpoint 5a thereof to the rotation shaft 6. The magnetic plate with theuniaxially magnetic anisotropy has an easy axis direction in which themagnetic plate is easily magnetized and a hard axis direction in whichit is not easily magnetized and which direction is perpendicular to theeasy axis direction. More specifically, the rotor 5 rotates togetherwith the rotation shaft 6 and the easy axis direction of the magneticanisotropy changes along with the rotation thereof. Utilization of thechange in the easy axis direction of the magnetic anisotropy permits todetect an angle of rotation. There is an assumption that the magneticdirection coincides with the easy axis direction and the hard axisdirection coincides with the direction perpendicular to the magneticdirection. A magnetic permeability in the easy axis direction is largeand that in the direction perpendicular to the easy direction, i.e., inthe hard axis direction is small equally likely a magnetic permeabilityin a vacuum.

There is used a structure in which the rotor 5 is joined at the centralpoint 5a thereof to the rotation shaft 6 so that the rotor 5 rotatesalong with the rotation of the rotation shaft 6. However, there may beused another structure in which the rotor 5 may rotate on the plane ofthe disk member via three or more supporting rollers (an angle betweenthe lines connecting the central point and the respective adjacentsupporting points being less than 180 degrees) as provided for exampleon the side portion of the rotor 5, without providing the rotation shaft6.

The exciting coil 4b is connected to an alternating-current source 40 sothat an alternating-current is supplied to the coil. Supply of thealternating-current to the exciting coil 4b causes a magnetic field tobe generated in a perpendicular direction to the plane in the section3b. The magnetic field has the largest intensity in the vicinity of thecopper wire of the coil and the intensity thereof becomes small withdecreasing distance to the central of the section 3b. More specifically,the magnetic field with the large intensity is generated in a region 30in which the detection coil 4a and the exciting coil 4b are placedclosely to each other.

The magnetic field as excited by the exciting coil 4b generates avoltage in response to the above-mentioned magnetic field. The detectioncoil 4a causes a synchronized detection circuit 41 connected to thedetection coil 4a to detect the above-mentioned voltage. At this moment,a value of voltage as detected changes in response to an angle of therotor 5.

Now, the description will be given below of an principle of an angledetection of the angle detection apparatus according to the embodimentof the present innovation, with reference to FIG. 3. FIG. 3 shows thatthe stator 3 and the rotor are placed one on another, and the magneticmember of the rotor 5 has a uniaxially magnetic anisotropy of themagnetic anisotropic energy Ku, and the easy axis direction thereofinclines at an angle of Θ relative to the stator 3.

The exciting coil P1 and the detection coil S1 generate a magneticcoupling by the magnetic flux ϕ in their adjacent regions 30. When theangle Θ is 0 degrees, the magnetic coupling between the exciting coil P1and the detection coil S1 becomes the maximum due to the characteristicproperty in the easy axis direction and the output voltage from S1becomes the maximum. When the angle Θ is 90 degrees, the magneticcoupling becomes the minimum due to the characteristic property in thehard axis direction and the output voltage from S1 becomes the minimum.

As shown in FIG. 4(A), an excited magnetic field H, which is generatedin perpendicular to the linear portion of the adjacent region 30 of theexciting coil P1 may be divided into a magnetization easy axis directioncomponent H// and a magnetization hard axis direction component H⊥,which is in perpendicular to the magnetization easy axis directioncomponent H// so that the excited magnetic field H is placed betweenthese components H// and H⊥. FIGS. 4(B) and 4(C) show a magnetizationdistribution in a glamorization that reed-shaped magnetization areas aregenerated in parallel with the easy axis direction, in which a directionof magnetic walls is in parallel with the uniaxially magnetic anisotropyand density of the magnetic flux of a magnetic plate is in the directionof the magnetic walls, i.e., only the direction Ku. FIG. 4(B) shows thatJs in the diagonally right-up direction and Js in the diagonallyleft-down direction in a demagnetized state are the same and B//=0. FIG.4(C) shows a state in which the magnetization takes place in thediagonally right-up direction and B//>0.

As shown in FIG. 4(C), in a magnetization process of the magnetic plateof the combination of the reed-shaped magnetization areas, which are inparallel with the direction Ku, the width of the magnetization areaswith magnetization in the direction in parallel with H// increases andthe width of the magnetization areas, which is not in parallel with itdecreases. The density of the magnetic flux of the magnetic plate isonly in the Ku direction, and there may be represented as “B//=μH// ”.With respect to all the magnetic moment, there may be represented as“B⊥=0” based on the model, which is in parallel with the easy axisdirection or not in parallel with it. The component, which intersectsthe linear portion of the detection coil S1 located in the adjacentregion 30, is the component in the Θ=0 direction of B// (perpendicularto the linear portion), and there may be represented as “B//cosΘ=μH//cos Θ=μH(cos Θ)².

If the magnetic fled is excited by the alternating-current with theangular frequency “ω”, there may be represented as “H=H₀ sin ωt ”,wherein H₀ being amplitude. Accordingly, the inductive voltage V₀ to thedetection coil S1 may be represented by “V₀=pμH₀(cos Θ)² sin ωt”,wherein “p” being a proportional constant concerning the number of turnsof the coil or the shape thereof. It is understood that the output ofthe angle detection apparatus 1 permits to provide an output voltage inproportion to the value of “(cos Θ)²”, by a synchronous demodulation todelete “H=H₀ sin ωt”. Actually, due to the magnetic plate having theuniaxial magnetic anisotropy, as well as a connection of the excitingcoil P1 and the detection coil S1 through the air, a certain output,which is not caused by “(cos Θ)²” may actually appear. This causes theoutput in 90 degrees or 270 degrees to become zero (see the outputvoltage waveform in FIG. 5).

The magnetic connection of the exciting coil P1 and the detection coilS1 may change in response to the degree Θ as described above, and theoutput voltage may change along with it. The magnetic connection maychange due to a size of the coil, a distance between the coil and therotor 5, a shape of the back yoke, etc. However, it may be representedby an appropriate coefficient, if the original shape is constant(excluding the rotation). As a result, the magnetic connection may berepresented, as a function of the angle Θ, as follows:k(Θ)=k₀ cos² Θ+k₁   Equation 1

wherein k₀ is a coefficient of the angle dependent component of themagnetic connection and k₁ being the component of the magneticconnection, which does not change in response to the angle.

The detection of an angle by the angle detection apparatus according tothe embodiment of the present innovation will be described based on theprinciple as describe above. FIG. 6 shows the angle detection of therotor. The respective views in FIG. 6 are viewed from the upper side ofthe angle detection apparatus 1, and the regions 3a, 3b of the stator 3,and the easy axis direction are showed in the form of lines, so as tofacilitate understanding. FIG. 6(A) shows zero degrees of the rotationangle, FIG. 6(B), 45 degrees of the rotation angle, and FIG. 6(C), 90degrees of the rotation angle. As described above, the rotor 5 has theuniaxial magnetic anisotropy, and the magnetic flux may be apt to passin the easy axis direction, but may not be apt to pass in the hard axisdirection.

More specifically, the direction of the magnetic fluxes as excited is inparallel to the easy axis direction of the rotor 5 (the angle θ beingzero degrees) in the region 30, which is the adjacent region between thedetection coil S1 and the exciting coil P1, as shown in FIG. 6(A), thenumber of magnetic fluxes, which intersect with the detection coil S1,increases, resulting in an increase in output. When the rotor 5 rotatesat an angle of 45 degrees, an angle between the direction of themagnetic fluxes and the easy axis direction of the rotor 5 is 45 degreesin the region 30, as shown in FIG. 6(B), with the result that themagnetic fluxes are not apt to pass unlikely the case in which the angleis zero degrees, thus leading to the smaller output accordingly. Whenthe rotor 5 rotates at angle of 90 degrees, the direction of themagnetic fluxes as excited is perpendicular to the easy axis directionof the rotor in the region 30, with the result that the number of themagnetic fluxes, which intersects with the detection coil S1, becomessmaller, thus leading to the smaller output. Detecting the magneticfluxes intersecting with the detection coil S1 and the value of voltagecorresponding to such intersecting fluxes, in response to the rotationangle of the rotor 5 makes it possible to obtain an angle of rotation ofthe rotor 5.

There is described the structure in which only the rotor 5 is rotatablyprovided by the rotation shaft 6 and the stator 3 and the back yoke 2are provided so as to face the disk member of the rotor. However, theremay be applied a structure in which the stator 3 and the back yoke 2 arerotatably provided by the rotation shaft 6. In this case, the stator 3has a hole, which has the same shape as the hole formed in the center ofthe rotor 5, in the center of the stator, and the coil is provided onthe outer periphery of the fan-shaped section so as to bypass theabove-mentioned hole. This causes the adjacent region 30 to be dividedinto two and the connection of the magnetic fluxes according to the easyaxis direction of the rotor 5 are generated in the respective dividedregions. For example, in FIG. 6, the rotation shaft 6 passes through thehole formed at the center, and the exciting coil and the detection coilare wound so as to bypass the through-hole. The adjacent regions 30 aredivided into two sub-regions. The stator side is not directly supportedto the rotation shaft 6, but is supported via bearings, etc., and fixedto the stationary unit.

In the preparation of the stator 3, the disk member may be divided intofan-shaped sections, and the exciting coil and the detection coil may bewound on the respective fan-shaped sections. Alternatively, the excitingcoil and the detection coil may be previously prepared so as to matchthe outer shape of the fan-shaped sections and they may be fixed to thedisk member. In addition, the coil may be formed by a printing method oran etching method. The fan-shaped section as divided may be provided ata part or whole of the linear portion thereof with coils or wires forexcitation so as to permit simultaneous flow of the electric current ina single direction, and the other fan-shaped section may be providedwith coils or wires for detection of the inductive voltage in the samemanner.

Concerning a method of creating the uniaxially magnetic anisotropy ofthe rotor 5, there may be applied various kinds of methods such as amethod of aligning narrow ribbon-shaped magnetic material or magneticwires on a non-magnetic substrate having a disk shape in a singledirection to create it (for example, closely-arranging amorphousmagnetic thin strips having the width of 1 mm and the thickness of 20 μmin parallel with each other and bonding them (see FIG. 7(A)), a methodof interweaving a magnetic material and a non-magnetic material throughthe length and breadth and impregnating them with a resin (see FIG.7(B)), a method of forming grooves in a magnetic material by an etchingprocess (see FIG. 7(C)), a method of plating a template prepared by anetching process (see FIG. 7(D)), a method of cutting for example adirectional silicon steel plate having a magnetic anisotropy in arolling direction or a permalloy or amorphous magnetic material having auniaxially magnetic anisotropy, which has been prepared by a heatingtreatment in a magnetic field, into a disk shape (see FIG. 7(E)).

According to the angle detection apparatus of the embodiment of thepresent innovation, the rotor 5 is formed of the disk member having theuniaxially magnetic anisotropy so as to provide a very simple structure,thus making it possible to manufacture the apparatus in a very easymanner, without the need of complicated processing.

In addition, the stator 3 is not provided so as to face the outersurface of the disk member, but provides a face structure in which thestator faces the plane of the disk member of the rotor 5, thuspermitting to decrease a thickness of the apparatus with a simplemanufacturing process, without deteriorating the function.

Further, the back yoke 2, which has substantially the same outer shapeas the disk member so as to face it, is provided on the opposite side tothe rotor relative to the stator 3, thus permitting to enhance themagnetic field to improve the detection sensitivity.

Second Embodiment of the Present Innovation

The angle detection apparatus according to this embodiment of thepresent innovation will be described with reference to FIGS. 8 to 10.FIG. 8 includes a set of views illustrating respective parts of theangle detection apparatus according to the second embodiment of thepresent innovation, FIG. 9 includes a set of views illustrating an angledetection by the angle detection apparatus according to the secondembodiment of the present innovation, and FIG. 10 is a view illustratingan output voltage waveform of the angle detection apparatus according tothe second embodiment of the present innovation.

The description, which overlaps with that according to the firstembodiment as described above, will be omitted in the description of theembodiment according to the second embodiment of the present innovation.

The angle detection apparatus according to this embodiment of thepresent innovation has a structure in which the stator formed of thedisk member is divided into four fan-shaped sections havingsubstantially the same outer shape, coils, which are wound along theouter periphery of the respective first fan-shaped section and thirdfan-shaped section, which constitute a set of fan-shaped sections of twosets of fan-shaped sections each of which face each other relative tothe central point of the disk member of the stator, are used as thedetection coil, and coils, which are wound along the outer periphery ofthe respective second fan-shaped section and fourth fan-shaped section,which constitute the other set of fan-shaped sections, are used as theexciting coil, and the exciting coils are wound so that the direction ofthe magnetic field excited by the exciting coil wound on the secondfan-shaped section and the direction of the magnetic field excited bythe exciting coil wound on the fourth fan-shaped section are opposite toeach other in polarity. A wire connection is made so that the detectioncoil wound on the first fan-shaped section and the detection coil woundon the third fan-shaped section are also in opposite to each other inpolarity. Here, the first fan-shaped section and the third fan-shapedsection constitute a set of sections that face each other relative tothe axis of the disk member of the stator, and the second fan-shapedsection and the fourth fan-shaped section constitute the other set ofsections that face each other relative to the axis of the disk member ofthe stator.

FIG. 8(A) is a top plan view of the back yoke 2 of the angle detectionapparatus according to this embodiment of the present innovation, FIG.8(B) is a top plan view of the stator 3 of the angle detection apparatusaccording to this embodiment of the present innovation and FIG. 8(C) isa top plan view of the rotor 5 of the angle detection apparatusaccording to this embodiment of the present innovation. In theembodiment of the present innovation, the stator 3 is divided into fourfan-shaped sections having substantially the same outer shape, as shownin FIG. 8(B), coils, which are wound along the respective outerperiphery of a set of fan-shaped sections, which is composed of thefirst fan-shaped section 3a and third fan-shaped section 3c, are used asthe detection coils 4a, 4c (referred also to as “S1” and “S2”,respectively), and coils, which are wound along the respective outerperiphery of the other set of fan-shaped sections, which is composed ofthe second fan-shaped section 3b and fourth fan-shaped section 3d, areused as the exciting coils 4b, 4d (referred also to as “P1” and “P2”,respectively). The respective coil is wound along the respectiveperiphery of the fan-shaped section with about 100 turns and has aheight of about 2 mm.

The exciting coils P1 and P2 are wound so that the directions of themagnetic fluxes, which are perpendicular to the direction of the planeof the stator 3, are opposite to each other (When one of them is anN-pole, the other becomes an S-pole) and a wire connection is made sothat the winding directions of the detection coils S1 and S2 areopposite to each other. This causes the detection soil S1 and theexciting coil P1, as well as the detection coil S2 and the exciting coilP2 to be placed in the easy axis direction of the uniaxial anisotropy ofthe rotor 5, in case where a rotation angle of the rotor 5 is zerodegrees, thus providing a strong connection. On the other hand, thedetection soil S1 and the exciting coil P1, as well as the detectioncoil S2 and the exciting coil P2 are placed in the hard axis directionof the uniaxial anisotropy of the rotor 5, thus providing about azero-connection.

An angle dependency of the connection coefficient “k ” between thedetection coil S1 and the exciting coil P1 as well as between thedetection coil S2 and the exciting coil P2, which are aligned in thevertical direction, respectively, may be represented by “k(Θ)=k₀ cos²Θ+k₁ (wherein, Θ being determined as zero degrees in the verticaldirection). The magnetic fluxes generated by the exciting coils arereferred to as “ϕ(P1)” and “ϕ(P2)”, respectively. The connection fromthe exciting coil P_(i) to the detection coil S_(j) is referred to as“k_(ji)(Θ)”. The output S1-S2 may be represented as follows:

$\begin{matrix}{{{S\; 1} - {S\; 2}} = {{j\;\omega\;{k_{11}(\theta)}{\phi\left( {P\; 1} \right)}} + {j\;\omega\;{k_{12}(\theta)}{\phi\left( {P\; 2} \right)}} - \left( {{j\;\omega\;{k_{21}(\theta)}{\phi\left( {P\; 1} \right)}} + {j\;\omega\;{k_{22}(\theta)}{\phi\left( {P\; 2} \right)}}} \right)}} & {{Equation}\mspace{14mu} 2} \\{\mspace{79mu}{{k_{11} = {k_{22} = {{k_{0}\cos^{2}\theta} + k_{1}}}},}} & \; \\{\mspace{79mu}{k_{12} = {k_{21} = {{k_{0}{\cos^{2}\left( {\frac{\pi}{2} - \theta} \right)}} + k_{1}}}}} & \;\end{matrix}$

From this equation, the output S1-S2 at an angle of zero degree may beexpressed as follows:S1−S2=jωk₀(ϕ(P1)−ϕ(P2))=2jωk₀ϕ(P1)(∵ϕ(P2)=−ϕ(P1))  Equation 3

and the value becomes maximum (corresponding to FIG. 9(A)). In thiscase, there is no influence of the output due to “k₁” on the output,because of subtraction of it. There is a relationship of“K₁₁=k₂₂=k₁₂=k₂₁” at an angle of 45 degrees, and S1-S2 becomes zero(corresponding to FIG. 9(B)). Only the connection by k₁₂, k₂₁ takesplace at an angle of 90 degrees, and the output S1-S2 (corresponding toFIG. 9(C)) may be represented as follows:S1−S2=jωk₀(ϕ(P2)−ϕ(P1))=−2jωk₀ϕ(P1)  Equation 4

In case of an angle of 135 degrees, the output becomes zero in the samemanner as 45 degrees (corresponding to FIG. 9(D)), and in case of anangle of 180 degrees, the value is the same as that with the inversedsign of the output at an angle of zero degrees (corresponding to FIG.9(E)). Consequently, an angle detection with a cycle of 180 degrees ispermitted. FIG. 10 shows the output results of the angle detectionapparatus according to this embodiment of the present innovation.

The back yoke 2 in this embodiment of the present innovation may be inthe form of a disk member having substantially the same outer shape asthe disk of the rotor 5, or be divided so as to cover at least therespective adjacent regions of the stators 3 divided into four.

In the angle detection apparatus according to this embodiment of thepresent application, the stator 3 is divided into four fan-shapedsections having substantially the same outer shape, the coils, which arewound around the outer peripheries of the set of the first fan-shapedsection 3a and the third fan-shaped section 3c facing each otherrelative to the axis of disk member of the stator 3 are used as thedetection coils 4a, 4c, the coils, which are wound around the outerperipheries of the other set of the second fan-shaped section 3b and thefourth fan-shaped section 3d facing each other are used as the excitingcoils 4b, 4d, and the direction of the magnetic field excited by theexciting coil 4b of the second fan-shaped section 3b is opposite inpolarity to the direction of the magnetic field excited by the excitingcoil 4d of the fourth fan-shaped section 3d. Therefore, utilization ofthe combination of the exciting coils 4b, 4d and the detection coils 4a,4c based on characteristic properties in the easy axis direction and thehard axis direction of the uniaxial anisotropy permits to make an angledetection with a cycle of 180 degrees.

Third Embodiment of the Present Innovation

The angle detection apparatus according to this embodiment of thepresent innovation will be described with reference to FIGS. 11 and 12.FIG. 11 includes a set of views illustrating respective parts of theangle detection apparatus according to the third embodiment of thepresent innovation and FIG. 12 includes a set of views showing outputresults of the angle detection apparatus according to the thirdembodiment of the present innovation.

The description, which overlaps with that according to the respectiveembodiments as described above, will be omitted in the description ofthe embodiment according to this embodiment of the present innovation.

The angle detection apparatus according to this embodiment of thepresent application has a structure in which the stator of the diskmember is divided into eight fan-shaped sections having substantiallythe same outer shape, of the eight fan-shaped sections as divided, atleast three fan-shaped sections are placed closely to each other so asto face the plane of the rotor in a combined state of the fan-shapedsections, and at least two detection coils and one exciting coil arewould alternately along the outer peripheries of the three fan-shapedsections, respectively. In addition, the back yoke is provided on theopposite side to the rotor relative to the stator so as to face the diskmember of the stator, and the back yoke is provided so as to cover atleast a place in which the fan-shaped sections as divided are placedclosely to each other.

FIG. 11(A) is a top plan view of the back yoke 2 of the angle detectionapparatus according to this embodiment of the present innovation, FIG.11(B) is a top plan view of the stator 3 of the angle detectionapparatus according to this embodiment of the present innovation, andFIG. 11(C) is a top plan view of the rotor 5 of the angle detectionapparatus according to this embodiment of the present innovation. Therotor 5 is formed of the disk member in the same manner as therespective embodiments as described above and has the uniaxial magneticanisotropy in the direction of the plane thereof. The rotation of therotor around the central point 5a in the plane of the disk may cause thedirection of magnetization to change. The stator 3 is formed by closelyplacing at least three fan-shaped sections of the eight fan-shapedsections having substantially the same outer shape into which the diskmember having substantially the same outer shape as the rotor 5 (thefan-shaped sections having a central angle of 45 degrees), as shown inFIG. 10(B) (the fan-shaped sections 3a˜3c).

The detection coil and the exciting coil are alternately wound on thethree fan-shaped sections 3a˜3c, respectively. In this embodiment, thedetection coil S1 is wound on the fan-shaped section 3a as divided, theexciting coil P1 is wound on the fan-shaped section 3b as divided, andthe detection coil S2 is wound on the fan-shaped section 3c as divided.

The back yoke 2 may be formed of the disk member having substantiallythe same outer shape as the rotor 5. The back yoke may be provided so asto cover the adjacent region between the detection coil S1 and theexciting coil P1, as well as the adjacent region between the excitingcoil P and the detection coil S2, which adjacent areas are required fora strong connection of the magnetic fields.

The formation of the stator 3 as shown in FIG. 11 causes a sinecomponent to be detected in one adjacent region between the detectioncoil and the exciting coil, and a cosine component to be detected in theother adjacent region. In case where an inductive voltage from theexciting coil P1 to the detection coil S1 is caused by the magneticconnection generated at an angle of the rotor 5 of 180 degrees, theinductive voltage from the exciting coil P1 to the detection coil S1causes the voltage, which is caused by the magnetic connection generatedat an angle of the rotor 5 of 135 degrees, to be detected.

More specifically, taking into consideration the difference incoefficient due to the difference in shape of the coil in comparisonwith the second embodiment as described above, the output voltage of thedetection coil S1 and the output voltage of the detection coil S2 may berepresented as follows:

$\begin{matrix}{{S\; 1} = {{j\;\omega\;{m_{11}(\theta)}{\phi\left( {P\; 1} \right)}} = {j\;{\omega\left( {{m_{0}\cos^{2}\theta} + m_{1}} \right)}{\phi\left( {P\; 1} \right)}}}} & {{Equation}\mspace{14mu} 5} \\{{S\; 2} = {{j\;\omega\;{m_{12}(\theta)}{\phi\left( {P\; 1} \right)}} = {j\;{\omega\left( {{m_{0}{\cos^{2}\left( {\theta + \frac{\pi}{4}} \right)}} + m_{1}} \right)}{\phi\left( {P\; 1} \right)}}}} & \;\end{matrix}$wherein, “m1” and “m0” being coefficients corresponding to “k1” and“k0”.

FIG. 12 shows the output waveform of the detection coil S1 and theoutput waveform of the detection coil S2, as well as the demodulatedwaveforms of them. FIG. 12(A) shows the output waveform of the detectioncoil S1, FIG. 12(B) shows the output waveform of the detection coil S2,and FIG. 12(C) shows the demodulated waveforms of these waveforms. Therespective waveforms have sine and cosine relationships as shown in FIG.12(C). More specifically, obtaining an arc tangent of the biphase outputvoltages makes it possible to detect precisely the angle in an easymanner utilizing dedicated integrated circuits, etc.

In the angle detection apparatus according to this embodiment of thepresent application, the stator 3 is divided into the eight fan-shapedsections having substantially the same outer shape, of the eightfan-shaped sections as divided, at least three fan-shaped sections areplaced closely to each other so as to face the plane of the rotor in acombined state of the fan-shaped sections, and two of the detectioncoils S1 and S2 and one of the exciting coil P1 are wound alternatelyalong the outer peripheries of the three fan-shaped sections asprovided. This makes it possible to detect accurately the sine componentand the cosine component by the minimum needed number of parts of thestator 3, thus providing an effect of detecting an angle of the rotor 5with a high degree of accuracy. Especially, the configuration in whichdedicated integrated circuits are used to obtain the arc tangent of thebiphase output voltage may provide an effect of simplifying amanufacturing process to improve the manufacture efficiency.

In addition, the back yoke 2 is provided on the opposite side to therotor 5 relative to the stator 3 so as to face the disk member of thestator 3, and the back yoke is provided so as to cover at least theplace in which the fan-shaped sections as divided are placed closely toeach other. This structure in which the back yoke 2 is placed only theregion having the strongest connection between the coils may provide aneffect of maintain a detection accuracy of angle by the minimum neededarea of the back yoke 2.

Fourth Embodiment of the Present Innovation

The angle detection apparatus according to this embodiment of thepresent innovation will be described with reference to FIGS. 13 and 14.FIG. 13 includes a set of views illustrating respective parts of theangle detection apparatus according to the fourth embodiment of thepresent innovation, and FIG. 14 is a top plan view in case where therespective parts of the angle detection apparatus according to thefourth embodiment of the present innovation are assembled together

The description, which overlaps with that according to the respectiveembodiments as described above, will be omitted in the description ofthe embodiment according to this embodiment of the present innovation.

In the angle detection apparatus according to this embodiment of thepresent application, the stator 3 is divided into sixteen fan-shapedsections having substantially the same outer shape, of a set of eightfan-shaped sections as placed closely to each other, a set of fourfan-shaped sections, which face each other in a cruciform relationshiprelative to the central point of the stator, detects a sine component,and other set of four fan-shaped sections detects a cosine component. Inaddition, a back yoke 2 is provided on the opposite side to the rotor 5relative to the stator 3, so as to face the disk member of the stator 3.The back yokes 2 is composed of eight fan-shaped sections havingsubstantially the same outer shape so as to correspond to the set ofeight fan-shaped sections of the stator 3. A gap is provided between therespective adjacent fan-shaped sections of the back yoke 2.

FIG. 13(A) is a top plan view of the back yoke 2 of the angle detectionapparatus according to this embodiment of the present innovation, FIG.13(B) is a top plan view of the stator 3 of the angle detectionapparatus according to this embodiment of the present innovation andFIG. 13(C) is a top plan view of the rotor 5 of the angle detectionapparatus according to this embodiment of the present innovation. In theembodiment of the present innovation, the stator 3 is divided intosixteen fan-shaped sections having substantially the same outer shape,as shown in FIG. 13, detection coils (S1˜S8) and exciting coils (P1˜P8)are would on the fan-shaped sections as placed adjacently so as to formeight sets of the stator ((3a, 3b), (3c, 3d), (3e, 3f), (3g, 3h), (3i,3j), (3k, 3l), (3m, 3n) and (3o, 3p)). The back yoke 2 is divided intothe eight fan-shaped sections (2a˜2h) so as to correspond these eightsets of the stator and a gap is provided between the respective adjacentfan-shaped sections of the back yoke.

The rotor 5 is formed of the disk member in the same manner as therespective embodiments as described above and has the uniaxial magneticanisotropy in the direction of the plane thereof. The rotation of therotor around the central point 5a in the plane of the disk may cause thedirection of magnetization to change.

FIG. 14 shows a state in which the back yoke 2, the stator 3 and therotor 5 as described above are combined in a stacked state. As shown inFIG. 14, one set of the fan-shaped sections (e.g., (3a, 3b) of thestator 3 corresponds to one fan-shaped section (e.g., 2a) of the backyoke and the back yoke 2 (the fan-shaped section 2a) enhances themagnetic connection of the set of the detection coil (e.g., S1) and theexciting coil (e.g., P1). The gap is provided between the adjacentfan-shaped sections of the back yoke for an area between the sets (e.g.,between the set (3a, 3b) and the set (3c, 3d)), resulting in anextremely weak connection between the detection coil (S2) and theexciting coil (P1).

More specifically, the configuration as shown in FIG. 14 enables thefour sets of fan-shaped sections ((3a, 3b), (3e, 3f), (3i, 3j), (3m,3n)), which are placed so as to face each other relative to the centralpoint in predetermined diameter directions of the disk member, to detecta sine component, and the other sets of fan-shaped sections ((3c, 3d),(3g, 3h), (3k, 3l), (3o, 3p)), which are placed so as to face each otherrelative to the central point in the other predetermined diameterdirections of the disk member, to detect a cosine component. Obtainingan arc tangent of the biphase output voltages makes it possible todetect precisely the angle in an easy manner utilizing dedicatedintegrated circuits, etc.

In the angle detection apparatus according to this embodiment of thepresent application, the stator 3 is divided into the sixteen fan-shapedsections having substantially the same outer shape, the exciting coilsand the detection coils are alternately wound on the adjacent fan-shapedsections and, of the eight fan-shaped sections as adjacently placed, thefour sets of fan-shaped sections, which are placed so as to face eachother in the predetermined diameter directions of the disk member, arecapable of detecting the sine component and the other four sets offan-shaped sections are capable of detecting the cosine component, thuspermitting to obtain an angle of rotation in an easy manner based onthese biphase signal. Particularly, a configuration of obtaining an arctangent of the biphase output voltages utilizing dedicated integratedcircuits, etc. make it possible to provide an effect of simplifying amanufacturing process to improve the manufacture efficiency.

In addition, the back yoke is divided into eight fan-shaped sectionshaving substantially the same outer shape so as to correspond to the setof eight fan-shaped sections of the stator, and the gap is providedbetween adjacent two of the fan-shaped sections. Consequently, the backyoke is placed only a region having the strongest connection between thecoils, thus permitting to provide effects of maintain a detectionaccuracy of angle by the back yoke composed of the minimum needed partsthereof

Fifth Embodiment of the Present Innovation

The angle detection apparatus according to this embodiment of thepresent innovation will be described with reference to FIG. 15. FIG. 15includes a set of views illustrating a stator of the angle detectionapparatus according to the fifth embodiment of the present innovation.

The description, which overlaps with that according to the respectiveembodiments as described above, will be omitted in the description ofthe embodiment according to this embodiment of the present innovation.

As shown in FIG. 15(A), in the angle detection apparatus according tothis embodiment, the stator 3 is divided into a plurality of fan-shapedsections (hereinafter referred to as the “divided fan-shaped sections”),and of the fan-shaped divided sections, the divided fan-shaped sections3a, 3b for excitation having a central angle of 45 degrees are providedso as to face each other relative to the center of the disk member (soas to be symmetrical with respect to the central point of the diskmember). The divided fan-shaped sections 3a, 3b for excitation areprovided at the respective outer peripheries thereof with exciting coils“+P” and “−P” so as to generate magnetic fields, which are opposite toeach other in polarity.

The two divided fan-shaped sections, which are placed adjacently to thedivided fan-shaped sections 3a, 3b for excitation and so as to face eachother relative to the center of the disk member, are used as the sinedetection fan-shaped sections 3c, 3d. The sine detection fan-shapedsections 3c, 3d are provided at the respective outer peripheries thereofwith detection coils “+S” and “−S” for detecting a signal of the sinecomponent so as to be opposite to each other in polarity.

The two divided fan-shaped sections, which are placed adjacently to thedivided fan-shaped sections 3a, 3b for excitation and so as to face eachother relative to the center of the disk member, so that the dividedfan-shaped sections 3a, 3b for excitation are placed between the sinedetection fan-shaped sections 3c, 3d, are used as the cosine detectionfan-shaped sections 3e, 3f. The cosine detection fan-shaped sections 3e,3f are provided at the respective outer peripheries thereof withdetection coils “+C” and “−C” for detecting a signal of the cosinecomponent so as to be opposite to each other in polarity.

The output of the sine component is detected a position with a symbol of“∘” as shown in FIG. 15 and the output of the cosine component isdetected a position with a symbol of “Δ” as shown in this figure. Thesine component “v” (S/P) of the sine component may be represented by:

$\begin{matrix}{{v\left( {S/P} \right)} = {2\; j\;\omega\;{\phi\left( {k_{0} + {k_{1}{\cos^{2}\left( {\theta + \frac{\pi}{4}} \right)}}} \right)}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$and the output V (C/P) of the cosine component may be represented by:v(C/P)=2jωϕ(k₀+k₁ cos²(θ))  Equation 7

In FIG. 15(A), the respective central angles of the sine detectionfan-shaped sections 3c, 3d and the cosine detection fan-shaped sections3e, 3f are set as 45 degrees and the fan-shaped sections 3g, 3h are setas the not-used area. However, the respective central angles of the sinedetection fan-shaped sections 3c, 3d and the cosine detection fan-shapedsections 3e, 3f may be set as 67.5 degrees as shown in FIG. 15(B).

The rotor 5 according to this embodiment of the present innovation isformed of the disk member in the same manner as the respectiveembodiments as described above and has the uniaxial magnetic anisotropyin the direction of the plane thereof. The rotation of the rotor aroundthe central point 5a in the plane of the disk may cause the direction ofmagnetization to change.

The back yoke 2 is provided on the opposite side to the rotor 5 relativeto the stator 3, so as to face the disk member of the stator 3. The backyoke 2 is formed of the disk member, which has the same outer shape asthe disk member of the stator 3.

Sixth Embodiment of the Present Innovation

The angle detection apparatus according to this embodiment of thepresent innovation will be described with reference to FIGS. 16 to 19.FIG. 16 includes the first set of views illustrating the stator of theangle detection apparatus according to the fifth embodiment of thepresent innovation, FIG. 17 includes the second set of viewsillustrating the stator of the angle detection apparatus according tothe fifth embodiment of the present innovation, FIG. 18 includes a setof views illustrating a back yoke of the angle detection apparatusaccording to the sixth embodiment of the present innovation, and FIG. 19includes a set of views showing output results of the angle detectionapparatus according to the sixth embodiment of the present innovation.

The description, which overlaps with that according to the respectiveembodiments as described above, will be omitted in the description ofthe embodiment according to this embodiment of the present innovation.

As shown in FIG. 16(A), in the angle detection apparatus according tothis embodiment, the stator 3 is divided into a plurality of fan-shapedsections (hereinafter referred to as the “divided fan-shaped sections”),and of the fan-shaped divided sections, the four divided fan-shapedsections 3a, 3b, 3c, 3d for excitation having a central angle of 45degrees are provided so as to face each other in a cruciformrelationship relative to the center of the disk member (so as to besymmetrical with respect to the central point of the disk member). Thedivided fan-shaped sections 3a, 3b, 3c, 3d for excitation are providedat the respective outer peripheries thereof with exciting coils “+P”(the divided fan-shaped sections 3a, 3d for excitation) and “−P” (thedivided fan-shaped sections 3b, 3c for excitation) so that the dividedfan-shaped sections for excitation (the divided fan-shaped sections 3a,3d for excitation, or the divided fan-shaped sections 3b, 3c forexcitation), which are placed so as to face each other relative to thecenter of the disk member, generate magnetic fields, which are oppositeto each other in polarity.

In addition, the four divided fan-shaped sections, which are placedadjacently to the divided fan-shaped sections 3a, 3b, 3c, 3d forexcitation and face each other in a cruciform relationship relative tothe center of the disk member, are used as the sine detection fan-shapedsections 3e, 3f, 3g, 3h. The sine detection fan-shaped sections 3e, 3f,3g, 3h are provided at the respective outer peripheries thereof withdetection coils “+S” (the sine detection fan-shaped sections 3e, 3f) and“−S” (the sine detection fan-shaped sections 3g, 3h) for detectingsignals of the sine component so that the sine detection fan-shapedsections (the sine detection fan-shaped sections 3e and 3g, or the sinedetection fan-shaped sections 3f and 3h), which are placed so as to faceeach other relative to the center of the disk member, are opposite toeach other in polarity.

Further, there are provided, as the cosine detection fan-shaped sections3i, 3j, 3k, 31, the four divided fan-shaped sections, which are placedso as to face each other in a cruciform relationship relative to thecenter of the disk member, and placed adjacently to the dividedfan-shaped sections 3a, 3b, 3c, 3d for excitation so that the dividedfan-shaped sections. 3a, 3b, 3c, 3d for excitation are placed betweenthe sine detection fan-shaped sections 3e, 3f, 3g, 3h, respectively. Thecosine detection fan-shaped sections 3i, 3j, 3k, 3l are provided at therespective outer peripheries thereof with detection coils “+C” (thecosine detection fan-shaped sections 3k, 3l) and “−C ” (the cosinedetection fan-shaped sections 3i, 3j) for detecting signals of thecosine component so that the cosine detection fan-shaped sections (thecosine detection fan-shaped sections 3i and 3k, or the cosine detectionfan-shaped sections 3j and 3l), which are placed so as to face eachother relative to the center of the disk member, are opposite to eachother in polarity.

The output of the sine component is detected a position with a symbol of“∘” as shown in FIG. 16 and the output of the cosine component isdetected a position with a symbol of “Δ” as shown in this figure. Morespecifically, such a structure enables only the connection between theadjacent exciting coil and detection coil (between ±P and ±S, andbetween ±P and ±C) to be made and disables the connection between thedetection coils (between ±S and ±C) from being made.

On the assumption that the output voltages from the respective coils are“v(Si/Pj)”, “v(Ci/Pj)”(wherein, “I” being the number of the detectioncoil, “j”, the number of the exciting coil), the output voltages “v” ofthe sine component may be represented as follows:

$\begin{matrix}{{v\left( {S_{1}/P_{1}} \right)} = {j\;\omega\;{\phi\left( {k_{0} + {k_{1}{\cos^{2}\left( {\theta - \frac{\pi}{4}} \right)}}} \right)}}} & {{Equation}\mspace{14mu} 8} \\{{v\left( {S_{2}/P_{2}} \right)} = {{- j}\;\omega\;{\phi\left( {k_{0} + {k_{1}{\cos^{2}\left( {\theta - \left( {\frac{\pi}{4} + \frac{\pi}{2}} \right)} \right)}}} \right)}}} & \; \\{{v\left( {S_{3}/P_{3}} \right)} = {j\;\omega\;{\phi\left( {k_{0} + {k_{1}{\cos^{2}\left( {\theta - \frac{\pi}{4}} \right)}}} \right)}}} & \; \\{{v\left( {S_{4}/P_{4}} \right)} = {{- j}\;\omega\;{\phi\left( {k_{0} + {k_{1}{\cos^{2}\left( {\theta - \left( {\frac{\pi}{4} + \frac{\pi}{2}} \right)} \right)}}} \right)}}} & \;\end{matrix}$

The sine output may be obtained from the sum of the voltages as follows:Equation 9v(S₁/P₁)+v(S₂/P₂)+v(S₃/P₃)+v(S₄/P₄)=2jωk₁ sin(2θ)  (1)

The output voltages “v” of the cosine component may be represented inthe same manner as follows:

$\begin{matrix}{{v\left( {C_{1}/P_{1}} \right)} = {j\;\omega\;{\phi\left( {k_{0} + {k_{1}{\cos^{2}\left( {\theta - \frac{\pi}{2}} \right)}}} \right)}}} & {{Equation}\mspace{14mu} 10} \\{{v\left( {C_{2}/P_{2}} \right)} = {{- j}\;\omega\;{\phi\left( {k_{0} + {k_{1}{\cos^{2}(\theta)}}} \right)}}} & \; \\{{v\left( {C_{3}/P_{3}} \right)} = {j\;\omega\;{\phi\left( {k_{0} + {k_{1}{\cos^{2}\left( {\theta - \frac{\pi}{2}} \right)}}} \right)}}} & \; \\{{v\left( {C_{4}/P_{4}} \right)} = {{- j}\;\omega\;{\phi\left( {k_{0} + {k_{1}{\cos^{2}(\theta)}}} \right)}}} & \;\end{matrix}$

The cosine output may be obtained from the sum of the voltages asfollows:Equation 11v(C₁/P₁)+v(C₃/P₃)+v(C₂/P₂)+v(C₄/P₄)=−2jωθk₁ cos(2θ)  (2)

In the structure as shown in FIG. 16(A), the central angle of thedivided fan-shaped sections 3a, 3b, 3c, 3d for excitation is set as 45degrees and the central angle of the sine detection fan-shaped sections3e, 3f, 3g, 3h and the cosine detection fan-shaped sections 3i, 3j, 3k,31 is set as 22.5 degrees. However, the central angle of the sinedetection fan-shaped sections 3e, 3f, 3g, 3h and the cosine detectionfan-shaped sections 3i, 3j, 3k, 31 may be set as an angle equal to orless than 22.5 degrees, as shown in FIG. 16(B), as long as they areplaced adjacently to the divided fan-shaped sections 3a, 3b, 3c, 3d forexcitation.

In addition, the combination of the symbols (+, −) may not be limitedonly to that as shown in FIG. 16. There suffices a structure in which acoefficient “k₀”, which is not dependent from the angle in Equations (1)and (2) as indicated above, may be cancelled as shown for example inFIGS. 17(A), (B), and there suffices an arrangement and polarity inwhich the value “k₀” may be cancelled by adding or subtracting the valueof “v(Si/Pj)” or “v(Ci/Pj)”. More specifically, there suffices astructure in which the exciting coils are composed of two coils having apositive polarity and two coils having a negative polarity, two coils ofthe coils for detecting the sine component are placed so as to bepositive, and the other two coils are placed so as to be negative, andtwo coils of the coils for detecting the cosine component are placed soas to be positive, and the other two coils are placed so as to benegative. The combination as described above makes it possible to detectsimultaneously the sine component and the cosine component by adjustingthe addition or subtraction (a wire connection) of “v(Si/Pj)” or“v(Ci/Pj)”. Making the fan-shaped sections, which are provided so as toface each other relative to the central point of the stator (so as to besymmetrical with respect to the central point), opposite to each otherin polarity as shown in FIGS. 16 and 17, permits the fluxes of theexciting coils to be restricted, thus preventing them from beingexpanded far to make it hard to cause interference with the otherdevice. In addition, concerning the detection coil, an influence of theexternal magnetic noise may cause inductive voltages which have the sameintensity and are opposite to each other in polarity, in the set of twoopposing detection coils, and they may be cancelled by a wire connectionin series. Therefore, it is preferable to place the fan-shaped sectionsto face each other relative to the central point of the stator so as tobe opposite to each other in polarity.

The rotor 5 in this embodiment of the present innovation is formed ofthe disk member in the same manner as the respective embodiments asdescribed above and has the uniaxial magnetic anisotropy in thedirection of the plane thereof. The rotation of the rotor around thecentral point 5a in the plane of the disk may cause the direction ofmagnetization to change.

The back yoke 2 is provided on the opposite side to the rotor 5 relativeto the stator 3, so as to face the disk member of the stator 3. The backyoke 2 may be formed of the disk member, which has the same outer shapeas the disk member of the stator 3. Alternatively, the back yoke 2 maybe provided at an adjacent position between the divided fan-shapedsection for excitation and the sine detection divided fan-shaped sectionor the cosine detection divided fan-shaped section, as shown in FIG. 18.The back yoke 2 may have the plate-like shape as shown in FIG. 18(A) ora semicylindrical shape as shown in FIG. 18(B).

FIG. 19 includes a set of views showing output results of the angledetection apparatus according to the sixth embodiment of the presentinnovation. Here, the coil is of 100 turns. In FIG. 19(A), an ordinateis indicative of an output voltage, and an abscissa is indicative of anangle in which the mechanical angle of 180 degree is represented as“100”. FIG. 19(B) shows an angle in which the value of an arc tangent(sin/cos) is calculated based on the output as shown in FIG. 19(A). Asis clear from these results, the respective waveforms of FIG. 19(A) areindicative of outputs of the sine component and the cosine component,and obtaining the arc tangent of these biphase output voltages makes itpossible to detect precisely the angle in an easy manner utilizingdedicated integrated circuits, etc.

Seventh Embodiment of the Present Innovation

The angle detection apparatus according to this embodiment of thepresent innovation will be described with reference to FIGS. 20 to 22.FIG. 20 is a cross-sectional view of the angle detection apparatusaccording to the seventh embodiment of the present innovation, FIG. 21is the first view illustrating a structure of the stator and the rotorof the angle detection apparatus according to the seventh embodiment ofthe present innovation, and FIG. 22 is the second view illustrating astructure of the stator and the rotor of the angle detection apparatusaccording to the seventh embodiment of the present innovation.

The description, which overlaps with that according to the respectiveembodiments as described above, will be omitted in the description ofthe embodiment according to this embodiment of the present innovation.

The angle detection apparatus according to this embodiment of thepresent innovation uses the two stators, as shown in FIG. 8(B), todetect the sine component and the cosine component. FIG. 20 shows thecross-section of the angle detection apparatus. The rotor 5 is jointedat the central point thereof to the rotation shaft 6 so that the rotor 5rotates along with the rotation of the rotation shaft in the plane ofthe disk member. The stators 31, 32 having substantially the same outershape are placed so as to face the disk member of the rotor 5 in anon-contact state. The back yoke 2 may be provided in a contact ornon-contact state with the stator, so as to face the surface of thestator 3 on the opposite side of which surface the rotor 5 is placed.

FIG. 21 shows an arrangement of the stators 31, 32 and the rotor 5,which are shown in FIG. 20. As shown in FIG. 21, the stators 31, 32(each of which is composed of four divided fan-shaped sections havingthe central angle of 90 degrees) as shown in FIG. 8(B) are placed with ashifted phase of 45 degrees in the respective plane. The rotor 5 havinga uniaxially magnetic anisotropy rotates between the stators 31, 32,with the result that the one stator detects the sine component and theother stator detects the cosine component. The stators 31, 32 arecapable of detecting the component of suppressing the modulation wave.Therefore, by the angle detection apparatus according to this embodimentof the present innovation, it is possible to make an angle detectionwith an extremely high degree of accuracy.

The angle detection apparatus according to this embodiment of thepresent innovation may have the structure as shown in FIG. 22 indicatedbelow. In the structure as shown in FIG. 20, the stators 31, 32 areprovided with an aligned phase, and the rotor 5 is placed between thestators 31, 32 with a shifted uniaxial anisotropy of 45 degrees in aplane and bonded to the stators. The anisotropy of the rotor 5 isshifted by an angle of 45 degrees, with the result that the rotation ofthe rotor enables the sine component to be detected by the one stator,and the cosine component to be detected by the other stator.

In the respective embodiments as described above of the presentinnovation, the exciting coil and the detection coil may be provided onthe whole of the side surface of the fan-shaped sections of the stator,or provided only in at least linear portion.

The respective embodiments of the present innovation have been describedabove. However, the scope of the present innovation is not limited onlyto the ranges described in the embodiments and various alternatives ormodifications to these embodiments of the innovation may be employed.

Eighth Embodiment of the Present Innovation

The angle detection apparatus according to this embodiment of thepresent innovation will be described with reference to FIG. 23. FIG. 23includes a set of views illustrating a stator of the angle detectionapparatus according to the eighth embodiment of the present innovationand illustrating a cross-section thereof.

The description, which overlaps with that according to the respectiveembodiments as described above, will be omitted in the description ofthe embodiment according to this embodiment of the present innovation.

The angle detection apparatus according to this embodiment of thepresent innovation, which uses two stators 3 to detect the sinecomponent and the cosine component in the same manner as the angledetection apparatus according to the seventh embodiment of the presentinnovation. As shown in FIG. 23(A), there is used a unit in which thestators divided into four as shown in FIG. 8 are bonded with a shiftedangle of 45 degrees (stators 31, 32), and the rotor 5 and the back yoke2 are provided so as to face the stators as shown in FIG. 23(B). Anelectric current for excitation of for example sin ωt is input to asystem of P1, and an electric current for excitation of for example sin2ωt is input to a system of P2. At this time, a synchronized detectionis made to prevent interference between sin ωt of the system P1 and sin2ωt of the system P2.

In FIG. 23, the frequency f2 of the system P2 is set as being twice asmuch as the frequency f1 of the system P1. However, the differentfrequencies of them (e.g., f1−f2>about 100 Hz) may provide a properseparation. Alternatively, there may be applied a configuration in whichthe electric current of sin ωt (or cos ωt) is input to the system P1 andthe electric current of cos ωt (or sin ωt) is input to the system P2.

There is a phase difference of 90 degrees caused between the voltageoutput from the system S1 and the voltage output from the system S2, andthe phases thereof are used as the “sine phase” and the “cosine phase”,respectively. Such a configuration permits to obtain a sine waveformwith less distortion, thus achieving a high accuracy angle detectionapparatus.

Ninth Embodiment of the Present Innovation

The angle detection apparatus according to this embodiment of thepresent innovation will be described with reference to FIG. 24. FIG. 24includes a set of cross-sectional views of the angle detection apparatusaccording to the ninth embodiment of the present innovation.

The description, which overlaps with that according to the respectiveembodiments as described above, will be omitted in the description ofthe embodiment according to this embodiment of the present innovation.

The angle detection apparatus according to this embodiment of thepresent innovation is provided with a shield unit 7, which shields theapparatus from an external magnetic field at least in a radial directionthat may be caused in the angle detection apparatus according to therespective embodiments of the present innovation. FIG. 24(A) is across-sectional view of the angle detection apparatus according to thefirst to sixth embodiments of the present innovation and FIG. 24(B) is across-sectional view of the angle detection apparatus according to theseventh embodiment of the present innovation. It is preferable to formthe shield unit 7 by bending it outer edge so as to cover entirely therotor 5, the stator 3 and the back yoke 2, thus not only shielding theapparatus from the outer magnetic field at least in the radialdirection, but also shielding it from the outer magnetic field in aperpendicular direction to the radial direction (in the direction of therotation shaft).

The angle detection apparatus according to this embodiment of thepresent innovation permits to shield the apparatus from the externalmagnetic field, thus detecting an angle with a high degree of accuracy.

Tenth Embodiment of the Present Innovation

The angle detection apparatus according to this embodiment of thepresent innovation will be described with reference to FIG. 25. FIG. 25includes a set of cross-sectional views of the angle detection apparatusaccording to the tenth embodiment of the present innovation.

The description, which overlaps with that according to the respectiveembodiments as described above, will be omitted in the description ofthe embodiment according to this embodiment of the present innovation.

In the angle detection apparatus according to this embodiment of thepresent innovation, the diameter of the rotor 5 is smaller than thediameter of the stator 3 and the back yoke 2, unlike the angle detectionapparatus according to the embodiments as described above of the presentinnovation. FIG. 25(A) is a cross-sectional view of the angle detectionapparatus according to the first to sixth embodiments of the presentinnovation and FIG. 25(B) is a cross-sectional view of the angledetection apparatus according to the seventh embodiment of the presentinnovation. Such a structure permits to decrease a centrifugal force ofrotation applied to the rotor 5, thus reducing a load. Morespecifically, even if the rotor 5 rotates at a high speed, damage may beprevented. In addition to the prevention of damage of the rotor, it ispossible to limit an influence of the external magnetic field in theradial direction, thus detecting the angle with a high degree ofaccuracy.

Incidentally, the shield unit 7 may be deleted from the structure asshown in FIG. 25.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 angle detection apparatus    -   2 back yoke    -   3 stator    -   4 coil    -   4a detection coil    -   4b exciting coil    -   40 alternating-current source    -   41 synchronized detection circuit    -   5 rotor    -   5a central point    -   6 rotation shaft    -   7 shield unit

While various embodiments of the innovation have been particularly shownand described, it will be understood by those skilled in the art thatvarious changes in form and details may be made therein withoutdeparting from the spirit and scope of the innovation as defined by theappended claims.

What is claimed is:
 1. An angle detection apparatus comprisescomprising: a rotor in which a disk member comprising a magnetic bodyhas a magnetic permeability, which is uniaxially anisotropic along aplane of the disk member, said disk member being rotatable around acentral point in a plane of the disk member; and a stator comprising aplurality of coils, at least one of said coils being an exciting coilthat generates a magnetic field, and at least one of said coils of therest being a detection coil that intersects with the magnetic fieldexcited by said exciting coil to detect a voltage corresponding to anangle of rotation of said rotor; wherein said stator is disposed in avicinity of the disk member of said rotor so as to face the planethereof, said stator being divided into a plurality of sections and saidexciting coil and said detection coil being provided on at least linearportions of the sections, respectively, on an outer periphery of saidsections; said stator has substantially a same outer shape as the diskmember of said rotor, said stator being divided into a plurality offan-shaped sections and said exciting coil and said detection coil beingprovided alternately on at least linear portions of the fan-shapedsections, respectively, on an outer periphery of said fan-shapedsections.
 2. The angle detection apparatus as claimed in claim 1,wherein: said stator has substantially a same outer shape as the diskmember of said rotor, said stator being divided into a plurality offan-shaped sections and said exciting coil and said detection coil beingprovided alternately on at least linear portions of the fan-shapedsections, respectively, on an outer periphery of said fan-shapedsections.
 3. The angle detection apparatus as claimed in claim 2 1,further comprising: a back yoke that is provided on an opposite side tosaid rotor relative to said stator, said back yoke having substantiallya same outer shape as a disk member of said stator and being placed soas to face the disk member thereof.
 4. The angle detection apparatus asclaimed in claim 3, wherein: said stator is divided into four fan-shapedsections having substantially a same outer shape; coils, which areprovided on at least linear portions of the fan-shaped sections,respectively, on an outer periphery of a set of fan-shaped sections oftwo sets of fan-shaped sections each of which face each other relativeto a central point of a disk member of said stator, are used as thedetection coil, and coils, which are provided on at least linearportions of the fan-shaped sections, respectively, on an outer peripheryof other set of fan-shaped sections of said two sets of fan-shapedsections, are used as the exciting coil; and in the set of thefan-shaped sections on which said exciting coils are provided, theexciting coils are placed so as to generate a magnetic field in whichthe exciting coils provided on the respective fan-shaped sections areopposite to each other in polarity, and in the other set of thefan-shaped sections on which said detection coils are provided, thedetection coils are placed so that the detection coils provided on therespective fan-shaped sections are opposite to each other in polarity.5. The angle detection apparatus as claimed in claim 2 1, wherein: saidstator is divided into four fan-shaped sections having substantially asame outer shape; coils, which are provided on at least linear portionsof the fan-shaped sections, respectively, on an outer periphery of a setof fan-shaped sections of two sets of fan-shaped sections each of whichface each other relative to a central point of a disk member of saidstator, are used as the detection coil, and coils, which are provided onat least linear portions of the fan-shaped sections, respectively, on anouter periphery of other set of fan-shaped sections of said two sets offan-shaped sections, are used as the exciting coil; and in the set ofthe fan-shaped sections on which said exciting coils are provided, theexciting coils are placed so as to generate a magnetic field in whichthe exciting coils provided on the respective fan-shaped sections areopposite to each other in polarity, and in the other set of thefan-shaped sections on which said detection coils are provided, thedetection coils are placed so that the detection coils provided on therespective fan-shaped sections are opposite to each other in polarity.6. The angle detection apparatus as claimed in claim 5, wherein: thereare provided as said stator two stators between which said rotor isplaced, said stators facing said rotor; said stator is stationary with ashifted phase of 45 degrees in a plane.
 7. The angle detection apparatusas claimed in claim 5, wherein: there are provided as said stator twostators with a aligned phase, and said rotor is placed between the twostators with a shifted uniaxial anisotropy of 45 degrees in a plane andbonded to the stators.
 8. The angle detection apparatus as claimed inclaim 5, wherein: there are provided as said stator two stators with ashifted phase of 45 degrees in a plane, and said rotor is placed betweenthe two stators so that the stators face the plane of said rotor andbonded to the stators.
 9. The angle detection apparatus as claimed inclaim 2 1, wherein: said stator is divided into sixteen fan-shapedsections having substantially a same outer shape, of a set of eightfan-shaped sections as placed closely to each other, a set of fourfan-shaped sections, which face each other in a cruciform relationshiprelative to a central point of a disk member of said stator, detects asine component, and other set of four fan-shaped sections detects acosine component.
 10. The angle detection apparatus as claimed in claim9, further comprising: a back yoke that is provided on an opposite sideto said rotor relative to said stator, said back yoke havingsubstantially a same outer shape as the disk member of said stator andbeing placed so as to face the disk member thereof, said back yoke beingdivided into eight fan-shaped sections having substantially a same outershape in a corresponding manner to the set of eight fan-shaped sectionsof said stator, and a gap is provided between adjacent two of thefan-shaped sections.
 11. The angle detection apparatus as claimed inclaim 2 1, wherein: said stator comprises fan-shaped sections as dividedwhich is obtained by dividing the stator into a plurality of fan-shapedsections; four fan-shaped sections as divided each having a centralangle of 45degrees of said fan-shaped sections as divided beingprovided, as a fan-shaped section as divided for excitation, so as toface each other in a cruciform relationship relative to a central pointof said disk member, the exciting coils being provided on the at leastlinear portion so that a direction of a magnetic field, which passesthrough an inside of two fan-shaped sections as divided for excitationof said four fan-shaped sections as divided for excitation is positiveand a direction of a magnetic field, which passes through an inside ofother two fan-shaped sections as divided for excitation thereof isnegative; four fan-shaped sections as divided being provided, as a sinedetection fan-shaped section, so as to be adjacent to said fan-shapedsection as divided for excitation and so as to face each other in acruciform relationship relative to the central point of said diskmember, a sine detection coil, which detects a sine component, beingprovided on at least the linear portion, which is adjacent to saidfan-shaped section as divided for excitation, on an outer periphery ofthe sine detection fan-shaped section as provided, and two of said sinedetection coils being aligned in a positive direction and other two ofsaid sine detection coils being aligned in a negative direction; andfour fan-shaped sections as divided being provided, as a cosinedetection fan-shaped section, so as to be adjacent to said fan-shapedsection as divided for excitation on an opposite side to said sinedetection fan-shaped section via said fan-shaped section as divided forexcitation, and so as to face each other in a cruciform relationshiprelative to the central point of said disk member, a cosine detectioncoil, which detects a cosine component, being provided on at least thelinear portion, which is adjacent to said fan-shaped section as dividedfor excitation, on an outer periphery of the cosine detection fan-shapedsection as provided, and two of said cosine detection coils beingaligned in a positive direction and other two of said cosine detectioncoils being aligned in a negative direction.
 12. The angle detectionapparatus as claimed in claim 11, further comprising: a back yoke thatis provided on an opposite side to said rotor relative to said stator,said back yoke being provided so as to cover at least a close areabetween said fan-shaped sections as divided for excitation and said sinedetection coil, which are placed closely to each other, and a close areabetween said fan-shaped sections as divided for excitation and saidcosine detection coil.
 13. The angle detection apparatus as claimed inclaim 1, wherein: said stator is divided into eight fan-shaped sectionsas divided having substantially a same outer shape, of the eightfan-shaped sections as divided, at least three fan-shaped sections areplaced closely to each other so as to face the plane of said rotor in acombined state of the fan-shaped sections, and two of said detectioncoils and one of said exciting coil are provided alternately on at leastlinear portion of the fan-shaped sections, respectively, on an outerperiphery of said three fan-shaped sections as divided.
 14. The angledetection apparatus as claimed in claim 13, further comprising: a backyoke that is provided on an opposite side to said rotor relative to saidstator, said back yoke having substantially a same outer shape as thedisk member of said stator and being placed so as to face the diskmember thereof, said back yoke being provided so as to cover at least aplace in which the fan-shaped sections as divided are placed closely toeach other.
 15. The angle detection apparatus as claimed in claim 1,wherein: two fan-shaped sections having a central angle of 45 degrees,of a plurality of fan-shaped sections as divided, which is obtained bydividing a disk member having substantially a same outer shape as thedisk member of said rotor, are placed, as a fan-shaped section asdivided for excitation, so as to face each other relative to a centralpoint of said disk member, exciting coils are provided on at leastlinear portion thereof, respectively, on an outer periphery of saidfan-shaped section as divided for excitation so as to generate magneticfields, which are opposite to each other in polarity; two of thefan-shaped sections as divided being provided, as a sine detectionfan-shaped section, adjacently to said fan-shaped section as divided forexcitation, so as to face each other relative to a central point of saiddisk member, the detection coil that detects a sine component beingprovided on at least linear portion on an outer periphery of the sinedetection fan-shaped section, so as to be opposite to each other inpolarity; and two of the fan-shaped sections as divided being provided,as a cosine detection fan-shaped section, adjacently to said fan-shapedsection as divided for excitation, on an opposite side of said sinedetection fan-shaped section via the fan-shaped section as divided forexcitation so as to face each other relative to a central point of saiddisk member, the detection coil that detects a cosine component beingprovided on at least linear portion on an outer periphery of the cosinedetection fan-shaped section, so as to be opposite to each other inpolarity.
 16. The angle detection apparatus as claimed in claim 15,further comprising: a back yoke that is provided on an opposite side tosaid rotor relative to said stator, said back yoke being provided so asto cover at least a close area between said fan-shaped sections asdivided for excitation and said sine detection coil, which are placedclosely to each other, and a close area between said fan-shaped sectionsas divided for excitation and said cosine detection coil.
 17. The angledetection apparatus as claimed in claim 16, wherein: said back yoke hassubstantially a semicylindrical shape, one of edges thereof being placedadjacently to said fan-shaped sections as divided for excitation andother of the edges thereof being placed adjacently to said sinedetection coil or said cosine detection coil.